.box div{
    width: 50%;
    height: 100px;
    float: left;
}
.box div:nth-last-child(1){
    background-color: brown;
}
.box div:nth-last-child(2){
    background-color: hotpink;
}
.box div:nth-last-child(3){
    background-color: palegoldenrod;
}
.box div:nth-last-child(4){
    background-color: fuchsia;
}
.box div:nth-last-child(5){
    background-color: brown;
}
.box div:nth-last-child(6){
    background-color: yellow;
}